There is a long discussion about this study with the virologist Christian Drosten on a German podcast (transcript here: https://www.ndr.de/nachrichten/info/coronaskript134.pdf), though in german only.

He was quite skeptical about the study, in particular as it doesn't have randomized groups, and e.g. the age difference between control and treatment group was very large. He also didn't consider the virus concentration in the throat to be a good endpoint to measure as from their experiments they know that it goes down over time anyway, and the virus tends to move to the lungs.